This paper is to explore the preparation process of aluminide coating and study whether it can effectively inhibit the corrosion of liquid lead to CLAM steel. The aluminide coating was prepared on the surface of CLAM steel by pack cementation with the formulated penetrant and subsequent thermal diffusion and in-situ oxidation treatments. The effects of different aluminizing time and thermal diffusion time on the coating thickness were studied. The oxidation resistance and compatibility of the aluminide coating with liquid lead were evaluated by static oxidation test and liquid lead corrosion test, respectively. The phase composition of the coating as well as the microstructure and element distribution of the coating before and after liquid lead corrosion were analyzed by XRD, SEM and EPMA. The aluminide coating prepared by pack cementation+thermal diffusion+in-situ oxidation is mainly composed of about 30 μm FeAl phase layer and about 70 μm α-Fe(Al) solid solution layer. In the process of heat treatment, the Fe-Al phase in the coating underwent the transformation of Fe2Al5, FeAl2, FeAl, Fe3Al and α-Fe(Al) in turn due to the phenomenon of mutual diffusion between Al and Fe. After static oxidation at 600 ℃ for 120 h, the oxidation weight gain of the aluminide coating is 0.028 mg/cm2, which is one order of magnitude lower than that of the CLAM steel. The aluminide coating changed the oxidation kinetic curve of CLAM steel from a linear law to a parabolic law. After corrosion of liquid lead at 550 ℃ for 600 h and 1800 h, the corrosion weight gain of aluminide coating were 0.058 mg/cm2 and 0.077 mg/cm2 respectively, which was only about 1/120 of the CLAM steel. A loose and porous iron oxide layer was formed on the surface of CLAM steel, and the aluminide coating did not corrode significantly, but after 1800 hours of corrosion, the thickness of the Al2O3 layer gradually decreased with the continuous consumption of the surface aluminum content. The aluminide coating has good oxidation resistance and compatibility with liquid lead, which can effectively inhibit the corrosion of liquid lead to CLAM steel.